A dozen still critical after NZ shootings

At least a dozen people - including a four-year-old girl - are still fighting for their lives after the Christchurch massacre that left 49 people dead.

The girl has been flown to Auckland's Starship children's hospital for treatment, while two other children - a two-year-old boy and a 13-year-old boy - are in a stable condition in Christchurch Hospital.

Head of surgery, Dr Greg Robertson, told reporters on Saturday that 36 of the 48 injured people remain in hospital. At least seven have been discharged.

"Of the 36 patients that remain in hospital, 11 of them are in the intensive care unit, including one female aged in her mid-20s," he said,.

"All of those in ICU are what we would consider critically ill."

He said most of the wounded who were shot while at Friday prayers at two Christchurch mosques were men aged between 30 and 40.

Christchurch hospital, which has experience with major trauma following the two earthquakes, was put to the test with 12 operating theatres in use throughout the night to treat the wounded, many who have suffered "quite significant" injuries.

"We have had patients with injuries to most parts of the body that range from relatively superficial soft tissue injuries to more complex injuries involving the chest, the abdomen, the pelvis, the long bones and the head," Dr Robertson said.

"Many of the people will require multiple trips to theatre to deal with the complex series of injuries that they have."

Four patients died on their way into the hospital.

Australian man Brenton Tarrant, 28, appeared in court on Saturday charged with one count of murder and is likely to face more before he reappears on April 5.